The present invention relates to a wrapping apparatus.
Prior specification EP 0 544 312 A1 discloses a wrapping apparatus for winding a web of wrapping foil around an object to be packaged. This wrapping apparatus comprises a foil dispenser arranged to circulate along a ring-like endless track around the object to be packaged. In the prior-art apparatus the track is of a substantially elliptical form. The track comprises a straight track portion which passes through the center hole of the cylindrical object to be packaged. The straight track portion extends outside the hole to a distance from the end of the cylindrical object. The track also comprises a curved portion which forms a curved track between ends of the straight track portion and around the object to be packaged. The foil dispenser comprises a frame and a detachable and replaceable foil roll mounted on the frame. Furthermore, the foil dispenser comprises supporting elements for supporting the foil roll on the frame, and tensioning means for braking the delivery of foil from the roll to maintain a predetermined foil tension.
A special problem which arises from the form of the track is that, during wrapping, in certain parts along the track, the foil span (i.e. a portion of the foil extending between a support point, e.g. edge point, of the object to be packaged and the foil dispenser) does not lengthen, but, instead, becomes shorter. Therefore the foil web would slacken if the tensioning device would not eliminate the slack. In EP 0 544 312 A1, the foil tensioning device is a complicated mechanical foil storage device comprising a number of fixedly mounted deflecting rollers, a number of flexibly mounted deflecting rollers and loading means for flexibly applying to the flexibly mounted rollers a load acting in a direction away from the fixedly mounted rollers so as to maintain tension in a variable amount of foil web passing along a winding path around the deflecting rollers.
A problem with this prior-art apparatus is that the foil storage takes up a relatively large space in the foil dispenser. Moreover, the structure is heavy, complex and expensive. Especially in types of wrapping apparatus in which the foil dispenser should be as small as possible to be able to pass e.g. through the central hole of a foil roll, the large size of the prior-art structure leads to problems. The heavy weight again results in a necessity to use a foil dispenser drive mechanism and motor accordingly dimensioned.
An object of the present invention is to eliminate the drawbacks described above.
A specific object of the present invention is to present a wrapping apparatus in which the foil dispenser is as simple as possible, contains few components and is light and cheap.